I'm on cycle day 40 and no sign of my period..

Hi I'm Brittany, pretty new to glow. The last 3 periods I have been using this app and have been on exactly a 25 day cycle. I'm now on cycle day 40 and no period. I've taken 2 tests and they say negative. I have been extremely tired and getting really bad headaches, and have been a tiny bit crampy a couple days ago. Glow tells me I only have 3% chance of being pregnant, what's up with that? So what's the matter with me? Haha